What's their benchmark call? What about clock_gettime() versus gettimeofday() ?
-adrian On 2 January 2015 at 06:09, grarpamp <grarp...@gmail.com> wrote: > Some recent FreeBSD related questions in this app area. > > > ---------- Forwarded message ---------- > From: Yawning Angel <yawn...@schwanenlied.me> > Date: Fri, Jan 2, 2015 at 5:20 AM > Subject: Re: [tor-dev] gettimeofday() Syscall Issues > To: tor-...@lists.torproject.org > > > On Thu, 01 Jan 2015 23:42:42 -0500 > Libertas <liber...@mykolab.com> wrote: > >> The first two account for the bulk of the calls, as they are in the >> core data relaying logic. >> >> Ultimately, the problem seems to be that the caching is very weak. At >> most, only half of the calls to tor_gettimeofday_cached_monotonic() >> use the cache. It appears in the vomiting print statements that >> loading a single simple HTML page >> (http://www.openbsd.org/faq/ports/guide.html to be exact) will cause >> >30 gettimeofday() syscalls. You can imagine how that would >> >accumulate for an exit carrying 800 KB/s if the caching >> doesn't improve much with additional circuits. > > So while optimization is cool and all, I'm not seeing why this > specifically is the underlying issue. > > Each cell can contain 498 bytes of user payload. Looking at things > simplistically this is 800 KiB/s -> 1644 cells/sec, leaving you with > approximately 608 microseconds of processing time per cell. > > On my i5-4250U box, gettimeofday() takes 22 ns on Linux, and 2441 ns on > FreeBSD. I'm not sure how accurate the FreeBSD results are as it was > in a VirtualBox VM (getpid() on the same VM takes 124 ns). If someone > has a OpenBSD box they should benchmark gettimeofday() and see how long > the call takes. > > Taking the FreeBSD case (since we know that tor works fine on Linux), a > single gettimeofday() call takes approximately, 0.39% of the per-cell > processing budget. > > For reference (assuming gettimeofday() in *BSD really is this shit > performance wise), 7000 calls to gettimeofday() is 17.09 ms worth of > calls. > > The clock code in tor does need love, so I wouldn't object to cleanup, > but I'm not sure it's in the state where it's causing the massive > performance degradation that you are seeing. > > Regards, > > -- > Yawning Angel > > _______________________________________________ > tor-dev mailing list > tor-...@lists.torproject.org > https://lists.torproject.org/cgi-bin/mailman/listinfo/tor-dev > > _______________________________________________ > freebsd-performance@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-performance > To unsubscribe, send any mail to "freebsd-performance-unsubscr...@freebsd.org" _______________________________________________ freebsd-performance@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-performance To unsubscribe, send any mail to "freebsd-performance-unsubscr...@freebsd.org"
